METHOD FOR THE PRODUCTION OF SYNTHETIC LEATHER

Abstract

The present invention relates to a method for the production of synthetic leather, to synthetic leather produced by such a method as well as to the use thereof. In particular, the present invention relates to a method for the production of synthetic leather exhibiting a virtual three-dimensional pattern on its visible face, whereby the leather comprises platelet-shaped effect pigments.

Claims

1. Method for the production of synthetic leather having a back face and a visible face and exhibiting a virtual three-dimensional pattern on the visible face, wherein a) a release sheet having an upper surface carrying a three-dimensional pattern thereon is coated with b) a first layer containing platelet-shaped effect pigments and a polyurethane compound directly onto the upper surface of the release sheet, and the first layer is thereafter coated with c) at least one further layer comprising a polyurethane compound, and d) the further layer in a wet state is brought into contact with a substrate layer and laminated thereto, and e) the first and the at least one further polyurethane containing layers applied to the release sheet are solidified either singly after steps b) and d) or in combination with each other after step d), whereby a layered stack of solid layers of at least the further layer, the first layer and of the release sheet on the substrate layer is achieved, and thereafter f) the release sheet is removed from the layered stack, thereby revealing a surface of the first layer containing platelet-shaped effect pigments which exhibits a virtual two-dimensional pattern which is then coated with a coating composition comprising a moisture curing polyurethane compound and solidified in air for a time period of at least 10 hours to achieve a solid moisture cured polyurethane coating layer.

2. Method according to claim 1, characterized in that the platelet-shaped effect pigment is at least one of the group consisting of pearlescent pigments, interference pigments, metal pigments or metal effect pigments.

3. Method according to claim 1, characterized in that the platelet-shaped effect pigment is an optically variable pigment.

4. Method according to claim 1, characterized in that the platelet-shaped effect pigments exhibit a particle size in the range of from 1 to 200 m and an aspect ratio of at least 10.

5. Method according to claim 1, characterized in that the virtual two-dimensional pattern on the surface of the first layer containing platelet-shaped effect pigments in step f) is a pattern consisting of area elements and line elements, whereby the line elements are regularly or irregularly distributed between the area elements and wherein the size of the area elements is from 0.5 mm.sup.2 to 10 cm.sup.2.

6. Method according to claim 1, characterized in that at least two further polyurethane containing layers are applied onto the first polyurethane containing layer comprising the platelet shaped effect pigments and that one of the further polyurethane containing layers is a middle layer composed of a polyurethane foam.

7. Method according to claim 1, characterized in that the moisture curing polyurethane compound comprises at least a polyurethane pre-polymer having free NCO groups in the molecule.

8. Method according to claim 1, characterized in that the coating composition comprising the moisture curing polyurethane compound additionally comprises a hydroxyl group containing component having free OH groups in the molecule.

9. Method according to claim 1, characterized in that the coating composition containing the moisture curing polyurethane compound additionally comprises at least one dye or transparent organic or inorganic colour pigment.

10. Method according to claim 1, characterized in that the coating composition containing the moisture curing polyurethane compound is solidified at a temperature in the range of from 12 to 30 C. at a relative humidity of the air in the range of from 40 to 80%.

11. Method according to claim 1, characterized in that the moisture cured polyurethane coating layer exhibits a layer thickness in the range of from 250 m to 1000 m.

12. Synthetic leather having a back face and a visible face and exhibiting a virtual three-dimensional pattern on the visible face, characterized in that the synthetic leather is composed of a substrate layer having thereon a stack of polyurethane containing layers, where the polyurethane containing layer which is the furthermost layer from the substrate layer comprises platelet-shaped effect pigments and is covered on its upper surface by a moisture-cured polyurethane coating layer.

13. Synthetic leather according to claim 12, characterized in that the effect pigments are contained in the platelet shaped effect pigments containing layer in an amount of from 5 to 40 % by weight, based on the weight of the layer.

14. Synthetic leather according to claim 12, characterized in that the synthetic leather exhibits an optically variable colour in addition to the virtual three-dimensional pattern.

15. Clothes, belts, shoes, bags, playing balls, automotive parts, furniture or upholstery, comprising therein synthetic leather according to claim 12.

Description

EXAMPLES

Example 1

[0077] 50 g of a polyurethane resin compound (UR-1390N, product from Shanghai Huide Chemicals) is thoroughly mixed with 40 g of DMF and 10 g of Iriodin 305, (golden platelet shaped effect pigment based on mica, product of Merck KGaA, Darmstadt, Germany).

[0078] The resulting mixture is applied by a bar coater onto a release paper having a three-dimensional continuous rhombus pattern on its surface to give a continuous coating layer on this surface. The coated release paper is dried at 80 C. for 15 min.

[0079] 100 g of the polyurethane resin (UR-1390N) are then applied onto the dry coating on the coated release paper. As long as the polyurethane resin is still in an uncured state, a fibrous synthetic leather backing layer is laminated to the wet polyurethane layer. The resulting layer stack is dried at 80 C. for another 15 min.

[0080] After the layered stack is cooled down to ambient temperature, the release paper is removed from the layered stack of polyurethane layers on the fibrous backing layer. The surface of the polyurethane layer containing the effect pigment is revealed, which exhibits a virtually two-dimensional continuous rhombus pattern of golden colour exhibiting a moderate gloss.

[0081] The effect pigment containing polyurethane layer is thereafter coated by a bar coater with a moisture curing polyurethane resin (DS-8918B, product from Shanghai Duoshen Chemicals) having an isocyanate content of about 50 to 60%, based on the weight of the resin essentially composed of isocyanate and polyurethane. The moisture curing polyurethane coating results in a continuous layer which is cured under ambient conditions for 24 hours. The resulting synthetic leather exhibits on its visible face a continuous rhombus pattern having a distinct three-dimensional effect in a profound golden colour with strong gloss. The resulting moisture cured polyurethane top layer has a dry thickness of about 500 m.

Example 2

[0082] Example 1 is repeated with the proviso that 10 g of Colorstream T10-08 (platelet shaped optically variable effect pigment based on silica flakes, Product of Merck KGaA Darmstadt, Germany) is used instead of Iriodin 305.

[0083] The resulting synthetic leather exhibits a continuous virtually three-dimensional rhombus pattern of brilliant pink colour in a steep viewing angle and golden colour in a flat viewing angle. The upper surface of the synthetic leather is smooth, plane and glossy.

Example 3

[0084] Example 2 is repeated with the proviso that the moisture curing polymer resin composition is mixed with 2% by weight, based on the weight of the resulting coating composition, of a blue dye.

[0085] The resulting synthetic leather exhibits a continuous virtually three-dimensional rhombus pattern of brilliant lilac colour in a steep viewing angle and green colour in a flat viewing angle. The upper surface of the synthetic leather is smooth, plane and glossy.